The Science of Building Muscle – By Alex Dear MSc

This is a guest article written by an old school friend and occasional training partner Alex Dear. Alex has a Masters Degree in Chemistry and is currently studying for his Masters in Physiotherapy. He competes in weightlifting, is a mobile sports massage therapist, and a strength training enthusiast. If you like the article and want to hear more please let me know and I will ask him to write more content.

The Science of Building Muscle

For many years we have known that lifting heavy things increases your strength and muscle size. Recently we have begun to understand why this happens. I’d like to introduce you to an important word at this point: hypertrophy. Hypertrophy simply means increased muscle size (the process that gives you the beach body). Lifting weights is essential to improving body composition because of hypertrophy: FACT and below you’ll find out why.

How do my muscles get bigger?

Muscles have a complex structure made up of many fibres. They get bigger by increasing the number of muscle fibres or the size of each fibre. Both of these result in hypertrophy (aka gains). Increases in the number of fibres is thought to occur from high amounts of force at long muscle lengths. This has been proven in mice but we aren’t sure if this happens in humans.

Muscle fibres can increase in size in two ways, they increase in width (measured by cross sectional area) or length. Many studies have been able to confirm that muscle length increases with strength training in humans. This particularly happens at long muscle lengths during contractions where the muscle is actively lengthening under load (eccentric only). Researchers have also found that the width of individual muscle fibres increase after strength training. Increasing the muscle width is the main mechanism by which humans increase their muscle size and you get bigger biceps (and who doesn’t want that?). This requires an increase in protein content within the muscle which happens through muscle protein synthesis. This is why you need to eat adequate amounts of protein if you want to make gains! How much you say? Minimum 0.4g per kilogram of bodyweight every couple of hours (around 4-6 times per day), you’re welcome!

How do we stimulate hypertrophy?

Mechanical tension, muscle damage and metabolic stress are the three mechanisms that have been proposed. When you lift weights it’s thought that it causes damage to the muscle tissue by splitting the fibres and the build-up of toxins causes metabolic stress. However there is only strong evidence for the mechanical tension mechanism currently. There is a three-step process: 1) muscle fibres have inbuilt sensors that can tell when you pick up something heavy, 2) they send out stress signals and 3) this tells your body to build more muscle (provided you have enough available protein in the body). Eccentric contractions (actively lowering the weight against gravity) have been shown to cause more muscle damage. It seems as though there isn’t much correlation between the amount of tissue damage and hypertrophy. Therefore workouts that are more damaging will not cause more hypertrophy.

What happens with mechanical tension then?

Muscles experience tension when they contract actively and when they are passively stretched. Whether they are shortening, lengthening or staying the same length mechanical tension has been shown to be related to changes in muscle size. The speed at which the muscle contracts has been shown to be a key factor, the slower the speed the more tension each muscle fibre is exposed to resulting in more force production. With a heavier weight the movement will be slower and therefore create more tension. Fatigue also has a big impact on hypertrophy, as you get tired more muscle fibres need to be recruited and the contraction speed slows. This reduction in speed generates more mechanical tension on the muscle fibres and stimulates more muscle growth.

In Summary

There is a three step process to building muscle tissue, there is an initial stimulus which leads to signalling events and an increase in muscle protein synthesis. This causes the deposition of protein within the muscle fibres, increasing their size. Mechanical tension is the only mechanism which has been clearly shown to affect muscle growth. High amounts of mechanical tension is created by heavier weights and fatigue therefore if you want to grow your muscles you need to train at or close to failure. Metabolic stress and muscle damage may contribute to muscle growth but it is not clear how at this time.